1. Field of the Invention
This invention relates to immobilizing radioactive waste and more specifically, this invention relates to a method and construct for sequestering liquid radioactive waste.
2. Background of the Invention
The immobilization and disposition of liquid (both aqueous and nonaqueous) radioactive waste (LRW) and non-radioactive waste such as pump oil, spent solvent, and crude oil spills, remain a significant challenge for chemical and nuclear industries.
LRW has been mixed with polymers in efforts to immobilize the LRW. However, the resulting construct is nothing more than a loose aggregate. These constructs do not meet the requirements of the United States and some foreign jurisdictions for hardened waste necessary for land disposal wherein exterior casings are not utilized.
Strict United States guidelines (10 CFR Part 61) as promulgated by the Nuclear Regulatory Commission (NRC) for permanent land disposal of radioactive waste dictates a myriad of benchmarks for safe encapsulation and storage, including the following metrics:
Compressive strength,
Thermal cycling,
Irradiation,
Biodegradation,
Short term and long term leach tests,
Immersion tests,
Free liquids/bleeding, and
Flammability,
whereby actual size waste forms are tested.
To date, very few radiation encapsulation protocols exist to meet Part 61 requirements. This is partly because disposal scenarios of radioactive waste often include nonradioactive waste streams. For example, 90 to 95 percent of the primary loops of breeder reactors are sodium cooled. Pumps are required to circulate the molten sodium and pump oil is used to keep the pumps operational. As a result, the pump oil becomes contaminated and over time, this contaminated oil needs to be disposed of safely. Techniques for efficiently disposing of all of these waste streams together and at reasonable cost remain elusive.
Attempts to solidify LRW-polymer constructs with cement have had limited success. This is because the cement prevents polymerization from occurring. In addition, significant amounts of water can result in the destruction of cement through the polymer absorption process. Any monoliths generated therefore lack the rigidity and/or water repulsion requirements of the NRC and foreign NRC counterparts.
Some jurisdictions allow heterogeneous waste forms to be generated, whereby solidified LRW is placed into bags, with the bags subsequently encapsulated in cement.
A need exists in the art for a single method to simultaneously sequester aqueous and non-aqueous (e.g. organic) nonradioactive waste and radioactive waste. The method should be simple to deploy and rely on relatively inexpensive, nontoxic sequestration agents. The method should not require controlled atmospheres or high pressures or temperatures when treating organic waste forms.